This invention relates generally to fasteners and their use in mounting panels such as transparencies in the walls of vehicles; more specifically, the invention relates to "blind" fasteners and it also relates to their use in installing and/or replacing a window or a canopy or a similar panel in an aircraft or the like.
In the aviation industry it is well known that an aircraft canopy could be become damaged if the aircraft were traveling at a high rate of speed and the canopy were accidentally struck by a bird; of course, other damage to a windshield or the like could occur if the aircraft flew through a sandstorm. The risk of damage in these situations is especially a problem when an aircraft flies at low altitudes while landing or taking off, or while cruising at speeds which could typically range from 250 to 500 knots. If an aircraft canopy were accidentally damaged or needed to be changed for some reason, its prompt replacement might be essential in order for the aircraft to be returned to service in a timely manner. Unfortunately, the current methods for replacing a canopy are rather time-consuming, and they generally require at least two people--each with a separate tool--to tighten or untighten the plurality of small and easily mishandled nuts and bolts that are routinely used to attach the canopy to the airframe. Obviously, minimizing any potential installation delays would be important if an aircraft such as a military jet needed to be flown on a combat mission or the like; hence, a "quick-change" fastening device to speedily replace an aircraft canopy would be highly desirable in many situations, so that the aircraft could be quickly returned to its fully-operational, "ready" state.
One method of installing and replacing a canopy involves the use of polycarbonate bushings which are permanently mounted in a plurality of apertures around a peripheral edge of the canopy. The canopy is placed over the cockpit and a multitude of fastening bolts are inserted through associated bolt holes in the periphery of the airframe opening; the bolts also pass through the bushings in the canopy. Outside the cockpit, nuts and washers are placed over the ends of the bolts that protrude from the bushings. However, the standard way of tightening this type of fastener requires that one person be stationed inside the cockpit to turn and tighten the bolts, and another person must be stationed outside the cockpit to hold a wrench (or some other tool) over the nut to prevent it from turning. While handling these multiple-part fasteners, a person could accidentally drop a small nut or washer, with the result that a part could be lost in the aircraft frame or fall to the ground, thereby further delaying the installation or removal procedure. And if a part were lost inside the aircraft, the part might possibly interfere with the operation of a complex mechanical control system or the sensitive electronics of the aircraft. Also, it would be annoying for a pilot who is making high-speed flight manuevers (such as barrel rolls or loops), to see a loose fastener part being tossed around in the cockpit.
Another problem with this type of fastening device is that the bushing is hollow and shaped in such a way that a liquid (e.g., water, a solvent, de-icing liquid, etc.) could easily collect and stand inside the bushing housing. After a period of time, such liquids could cause a polycarbonate bushing material to deteriorate and crack. Accordingly, there has existed a need for a fastening device that helps seal out liquids and which is configured for a fastening a canopy or the like to an airframe--and which may be fastened or unfastened by only one person, so as to reduce the time and labor required to replace a canopy.
Various prior art devices have been proposed, of course, for fastening a canopy to an airframe, including Martin et al. U.S. Pat. No. 2,511,168 entitled "Construction and Mounting of Units of Transparent Synthetic Resins" and Stefanik U.S. Pat. No. 4,004,388 entitled "Window Panel Edge Construction." The Martin patent discloses a plexiglass canopy or panel structure having a bead around the peripheral edge of the panel. The panel has a socket that is adapted to receive a support structure formed from a wire mesh which is impregnated with a synthetic resin. However, to replace the Martin canopy and its associated support structure, a nut which is mounted exteriorly of the airframe and a bolt which is mounted interiorly of the airframe must generally be manipulated--by two persons. The Stefanik method suffers from some of the same drawbacks as the Martin installation method. That is, the Stefanik method also employs a plurality of nuts and bolts which are fastened around the peripheral edge of a windshield, in order to mount it over an opening in the aircraft fuselage. Of course, with the Stefanik fastener, one person could not easily attach a windshield over a frontal opening in an airframe.
Other prior art shown in Wagner et al. U.S. Pat. No. 2,258,724 entitled "Fixation of Window Panes in Aircraft" teaches a structure that is presumably adapted to mount a dome-shaped convex-concavo window pane in the outer wall of a pressurized compartment. Wagner's primary concern, however, seems to be that of mounting a pane (i.e., a canopy) in such a way that the connection between the canopy and the aircraft walls can withstand the stresses resulting from pressure and temperature differentials--especially when the aircraft is at high altitudes. Wagner teaches the use of a specially molded bead which is integrally formed around the edge portion of the pane; the bead is positioned so that it may be clamped between jaw-like holding members. Regrettably, with such a sophisticated and precisely formed fastening structure, each aircraft canopy would need a specially--and probably expensively--fabricated peripheral bead. And to hold such a canopy in position, custom built jaw-like fastening members would be required for each type of aircraft, thus further increasing the cost to manufacture such a structure. In other words, one jaw-like fastening member could not be readily used to mount different types of aircraft canopies, because each canopy would have its unique, specially shaped bead around the canopy edge.
There are other prior art devices which are related to aircraft canopies or windshield structures, including Littell, Jr. U.S. Pat. No. 4,081,581 entitled "Laminated Aircraft Windshield" and Bolte U.S. Pat. No. 2,637,076 entitled "Reinforced Canopy Structure." However, the Little patent focuses primarily on providing a laminated windshield which purportedlly functions as an energy absorber, so that forces emanating from an impact (such as a bird strike) would be dissipated without penetrating the windshield. And like the Martin and Stefanik fastening methods, Littell discloses a plurality of bolt holes which are provided around the edge of the windshield in order to fasten the windshield to the aircraft fuselage; thus, Littell's method also seems to require at least two persons to replace a windshield.
While most of the above devices have attempted to address the problem of securely mounting a canopy to an airframe, it seems that the designers of these prior art devices have not given as much attention as seems justified to the need to replace a canopy and to efficiently use time and manpower. Therefore, there has remained a need for a "quick-change" fastening device which may readily be fastened or unfastened by just one person, whereby an aircraft canopy may be efficiently replaced in a timely manner. It is an object of this invention to provide such a convenient fastening device.
Another object is to provide a fastener without loose parts (such as a nut and washer) in order to minimize the possibility of accidentally dropping any small parts and losing them in the aircraft or on the floor.
One other object is to provide a fastener which is constructed so that a significant amount of "floating action" may be provided between the canopy and the fuselage, in order to facilitate installation of the canopy--and to prevent stress concentrations from developing as a result of any difference in any expansion or contraction of the canopy and the fuselage.
Still another object is to provide a fastening device having a resilient or rubber-like cap that is sized and shaped to fit into the top of the housing, so as to assist in preventing liquids from collecting in the fastener housing.
One more object is to provide a fastening device having a planar outer surface so as to provide an aerodynamically smooth exposed surface when it is used to install a canopy or the like in an aircraft.
These and other objects will no doubt be apparent from a reading of the specification and claims, and from a study of the accompanying drawings illustrating certain facets of the invention.